JP7082541B2 - Repair welding method - Google Patents

Description

The present disclosure relates to a repair welding method.

After a member with a weld is used, repair welds may be performed for repair.
For example, in high-temperature piping of boilers and turbines in thermal / nuclear power plants, chemical plants, etc., creep damage may occur in welds due to long-term use.
In such a case, instead of replacing the entire pipe in which the creep damage has occurred, the portion where the creep damage has occurred is excised, and the excised portion is repair-welded (see Patent Document 1). ).

Special Publication No. 60-008148

In the repair welding method described in Patent Document 1, the heat-affected zone is formed by considering the extending direction of the heat-affected zone generated by the repair welding inside the weld metal of the present weld weld, that is, the weld metal of the existing weld. The stress acting is reduced.
By the way, in the region where the heat-affected zone of the existing weld and the heat-affected zone of the repair weld overlap, the existing weld is affected by heat both during welding and during repair welding. It has been found that the welded zone is more susceptible to damage due to the acting stress as compared to the region affected only by the heat of either the weld or the repair weld. Therefore, it is desirable to minimize the overlap between the heat-affected zone of the existing weld and the heat-affected zone of the repair weld. However, in the repair welding method described in Patent Document 1, the region where the heat-affected zone of the existing weld and the heat-affected zone of the repair weld overlap is not particularly mentioned.

In view of the above circumstances, at least one embodiment of the present invention aims to suppress the influence of the heat-affected zone of repair welding on the life of a member.

(1) The repair welding method according to at least one embodiment of the present invention is
It is a repair welding method for members in which the first end and the second end of the base metal are connected by welding.
A step of removing a portion including at least a part of the first heat-affected zone in the existing welded portion of the member.
The process of performing repair welding after removing the above-mentioned part, and
Equipped with
In the cross section including the base metal and the existing welded portion, the first heat-affected zone and the said The cross-sectional angle with the second heat-affected zone is 70 degrees or more and 110 degrees or less.

In the cross section including the base metal and the existing weld, the intersection of the first heat-affected zone and the second heat-affected zone due to repair welding in the existing weld is easily damaged by the acting stress as described above. It is desirable to prevent the intersection from occurring as much as possible. In the cross section including the base metal and the existing welded zone, the first heat-affected zone and the second heat-affected zone are formed with a certain width along the boundary surface in contact with the weld metal, respectively, so that the first heat-affected zone and the second heat-affected zone are formed. 2 If the intersection angle with the heat-affected zone is 90 degrees, the cross-sectional area of the intersection can be minimized, and the more the intersection angle deviates from 90 degrees, the larger the cross-sectional area of the intersection.
In that respect, according to the method (1) above, the intersection angle between the first heat-affected zone and the second heat-affected zone is 70 degrees or more and 110 degrees or less. It is possible to suppress an increase in the cross-sectional area of the intersection. As a result, it is possible to suppress a decrease in the life of the member due to repair welding.

(2) In some embodiments, in the method of (1) above,
In the cross section including the base material and the existing welded portion, the repair welding is performed from the base material on the first end side to the base material on the second end side.
The first heat-affected zone generated in the base material on the first end side and the base material on the second end side before removing the portion including at least a part of the first heat-affected zone. The second heat-affected zone generated on the base material on the first end side and the second end portion with respect to the first distance on the surface of the base material between the first heat-affected zone and the first heat-affected zone. The second distance on the surface of the base material with the second heat-affected zone generated on the base material on the side is 1.1 times or more and 2.0 times or less the first distance.

According to the method (2), since the second interval is 1.1 times or more the first interval, the first heat-affected zone and the second heat-affected zone overlap in the vicinity of the surface of the base metal. Can be suppressed. Further, according to the method (2), since the second interval is 2.0 times or less the first interval, the range of repair welding can be suppressed.

(3) In some embodiments, in the method (1) or (2) above,
In the cross section including the base material and the existing welded portion, the repair welding is performed from the base material on the first end side to the base material on the second end side.
The third distance between the intersection on the first end side and the intersection on the second end side is the second heat from the surface of the weld metal of the repair weld in the second heat-affected zone. The position on the first end side, which is 0.8 times the maximum depth to the affected area, and the position on the second end side, which is 0.8 times the maximum depth. It is less than or equal to the fourth interval.

According to the method (3) above, the depth of the intersection on the first end side and the intersection on the second end side, that is, the depth from the surface of the weld metal in the repair weld is determined by the weld metal in the repair weld. The depth from the surface to the second heat-affected zone can be 0.8 times or more the maximum value. As a result, in the cross section including the base metal and the existing welded portion, the position in the depth direction of the intersection on the first end side and the intersection on the second end side is set to the deepest position in the second heat-affected zone. You can get closer. Therefore, the extending direction of the second heat-affected zone at the intersection on the first end side and the intersection on the second end side can be brought closer to the direction orthogonal to the depth direction. Therefore, if the first heat-affected zone at the intersection extends in substantially the same direction as the depth direction, the above-mentioned intersection angle at the intersection can be approached to 90 degrees, and the cross-sectional area of the intersection becomes large. Can be suppressed.

(4) In some embodiments, in any of the methods (1) to (3), the repair welding is performed on the weld metal of the existing weld in the cross section including the base metal and the existing weld. The cross-sectional angle between the extending direction of the generated second heat-affected zone and the thickness direction of the member is 70 degrees or more and 110 degrees or less.

The second heat-affected part generated by repair welding on the weld metal of the existing weld, that is, the second heat-affected part in the weld metal of the existing weld is affected by the second heat-affected part of the base metal and the heat of the repair weld. It is more susceptible to damage due to the applied stress than the weld metal of an existing weld that has not been subjected to. Therefore, when a tensile stress acts on the above member in a direction in which the first end side and the second end side are separated from each other, the existing welded portion when viewed from the direction in which the tensile stress acts. It is desirable that the projected area of the second heat-affected zone in the weld metal is small.
In that respect, according to the method (4) above, in the cross section including the base metal and the existing welded portion, the extending direction of the second heat-affected zone in the weld metal of the existing welded portion and the thickness direction of the member. Since the intersection angle with and is 70 degrees or more and 110 degrees or less, the extending direction of the second heat-affected zone in the weld metal of the existing weld approaches the direction in which the above-mentioned tensile stress acts, and the above-mentioned projected area can be suppressed. ..

(5) In some embodiments, in any of the methods (1) to (4) above, the weld toe of the repair weld is present in the base metal.

According to the method (5) above, the region of the second heat-affected zone in the weld metal can be reduced as compared with the case where the weld toe portion of the repair weld is present in the weld metal of the existing weld.

(6) In some embodiments, in the method (1) above,
In the cross section including the base metal and the existing welded portion, the repair welding is performed from the base metal on the first end side to the weld metal of the existing welded portion.
The intermediate position between the position of the second heat-affected zone appearing on the surface of the base metal on the first end side and the position of the second heat-affected zone appearing on the surface of the weld metal of the existing welded portion is It exists in the weld metal of the existing welded zone before removing the portion including at least a part of the first heat-affected zone.

According to the method (6) above, the removal amount in the step of removing the portion including at least a part of the first heat-affected zone while suppressing the increase in the cross-sectional area of the intersection, and the welding by repair welding. The volume of metal can be reduced, and the man-hours for repair welding can be reduced.

(7) In some embodiments, in the above methods (1) to (6),
Prior to the repair welding step, the step of measuring the shape of the first heat-affected zone and the step of measuring the shape of the first heat-affected zone
Based on the shape of the first heat-affected zone measured in the step of measuring the shape of the first heat-affected zone, the removal range in the step of removing the portion including at least a part of the first heat-affected zone is determined. Process and
Further prepare.

According to the method (7) above, a portion including at least a part of the first heat-affected zone is provided so that the intersection angle between the first heat-affected zone and the second heat-affected zone is 70 degrees or more and 110 degrees or less. You will be able to remove it. As a result, it is possible to suppress an increase in the cross-sectional area of the cross section in the cross section including the base metal and the existing welded portion, and it is possible to suppress a decrease in the life of the member due to repair welding.

(8) In some embodiments, in the method (7) above, in the step of measuring the shape of the first heat-affected zone, the shape of the first heat-affected zone is measured by ultrasonic flaw detection by a phased array method. Or, the shape of the first heat-affected zone is exposed by etching, and the shape of the first heat-affected zone is measured.

According to the method (8) above, the shape of the first heat-affected zone can be measured nondestructively by measuring the shape of the first heat-affected zone by ultrasonic flaw detection by the phased array method. Further, according to the method (8) above, the shape of the first heat-affected zone can be easily measured by making the shape of the first heat-affected zone appear on the surface of the member by a simple method of etching.

(9) In some embodiments, in any of the methods (1) to (8) above, the base material is a high-strength ferritic heat-resistant steel.

The method (9) above is suitable for repair welding of a member whose base material is made of high-strength ferritic heat-resistant steel.

(10) In some embodiments, in any of the methods (1) to (9) above, the member is a boiler pipe.

The method (10) above is suitable for repair welding of boiler piping.

According to at least one embodiment of the present invention, the influence of the heat-affected zone of repair welding on the life of the member can be suppressed.

It is a figure which shows a part of the piping as an example of the member to which the repair welding method which concerns on some embodiments is applied. It is a figure which shows a part of the cross section of a pipe including a base material and an existing weld part schematically. It is a flowchart which shows the procedure of the process of the repair welding method which concerns on some Embodiments. It is a figure which shows an example about a part of the cross section of a pipe including a base metal and an existing weld part, (a) is a figure which shows the macrostructure of a cross section, and (b) is an ultrasonic wave by a phased array method of the cross section. It is a contour diagram which shows the result of a flaw detection. It is a figure which shows an example of the surface of a pipe after performing micro-etching. It is a figure which shows the part of the cross section of a pipe after removing the removal area in the removal step S30 schematically. It is a figure which shows the part of the cross section of a pipe after removing the removal area in the removal step S30 schematically. It is a figure which shows the part of the cross section of a pipe after removing the removal area in the removal step S30 schematically. It is a figure which shows a part of the cross section of a pipe after repair welding schematically. It is a figure which shows a part of the cross section of a pipe after repair welding schematically. It is a figure which shows a part of the cross section of a pipe after repair welding schematically.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, but are merely explanatory examples. do not have.
For example, expressions that represent relative or absolute arrangements such as "in one direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a tolerance or a state of relative displacement at an angle or distance to the extent that the same function can be obtained.
For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, an expression representing a shape such as a square shape or a cylindrical shape not only represents a shape such as a square shape or a cylindrical shape in a geometrically strict sense, but also an uneven portion or a chamfering within a range where the same effect can be obtained. It shall also represent the shape including the part and the like.
On the other hand, the expressions "to have", "to have", "to have", "to include", or "to have" one component are not exclusive expressions that exclude the existence of other components.

FIG. 1 is a diagram showing a part of a pipe as an example of a member to which the repair welding method according to some embodiments is applied.
Members (objects) to which the repair welding method according to some embodiments are applied are, for example, high-temperature pipes for boilers and turbines in thermal power / nuclear power plants, chemical plants, and the like. In such a high temperature pipe (pipe) 1, there are a plurality of types of welded parts. For example, the high temperature pipe 1 has a circumferential welded portion for connecting the pipes and a pedestal welded portion for connecting the pipe and the branch pipe. Further, when the pipe 1 is manufactured from a plate-shaped member, as shown in FIG. 1, a longitudinal welded portion 10 extending in the pipe axis direction for connecting the ends of the plates as the base material is provided. exist.

A member such as the high temperature pipe 1 that is used for a long time in a high temperature and high pressure environment may have cracks due to creep damage in the welded portion, particularly the heat affected zone (HAZ portion). In the following description, a case where a crack is generated in the heat-affected zone of the longitudinal welded portion 10 of the pipe 1 will be described as an example. FIG. 2 is a diagram schematically showing a part of a cross section of a pipe 1 including a base material 2 and an existing welded portion 11. That is, FIG. 2 is a diagram schematically showing a part of a cross section (cross section seen from the pipe axis direction) of the pipe 1 cut in a direction orthogonal to the pipe axis direction. In FIG. 2, the left-right direction is the circumferential direction of the pipe 1, the upper side is the radial outside, and the lower side is the radial inside. In the following description, the longitudinal welded portion 10 that has existed before the repair welding is performed is referred to as an existing welded portion 11.

The existing welded portion 11 is a welded portion that connects the first end portion 3 and the second end portion 4 of the base material 2 of the pipe 1, and is affected by the heat during welding of the weld metal 5 and the existing welded portion 11. Includes the heat-affected zone 6 generated in the base metal 2 by receiving. In the pipe 1 shown in FIG. 2, it is assumed that a crack 7 is generated in the heat-affected zone 6 on the first end portion 3 side. The hoop stress acts mainly on the pipe 1 due to the pressure of the fluid flowing inside the pipe 1. Therefore, tensile stress mainly acts on the existing welded portion 11 in the circumferential direction, that is, in the left-right direction in FIG.

For example, in some embodiments, the pipe 1 is inspected during the periodic inspection of the plant. In the following description, a case where a crack 7 generated in the pipe 1 is found by a periodic inspection and the pipe 1 is repaired by repair welding will be described.
When a crack 7 is generated in the pipe 1, the pipe 1 can be repaired by removing a part of the region of the pipe 1 including the crack 7 and performing repair welding on the removed portion. However, by performing repair welding, a heat-affected zone affected by heat due to repair welding is generated in the pipe 1. In the following description, the heat-affected zone 6 generated in the base metal 2 by being affected by the heat during welding of the existing welded portion 11 is also referred to as a first heat-affected zone 6. The heat-affected zone generated by being affected by the heat during welding of the repair welded portion 21 (see FIGS. 9 to 11) is referred to as a second heat-affected zone 26 (see FIGS. 9 to 11).

For example, as shown in FIGS. 6 to 8 described later, when a part of the pipe 1 including the existing welded zone 11 is removed and then repair welding is performed as shown in FIGS. 9 to 11 described later, the first heat is generated. A region where the affected zone 6 and the second heat affected zone 26 overlap is generated. In the following description, this overlapping region will be referred to as an overlapping heat-affected zone 36.
The overlapping heat-affected zone 36 is affected only by the heat of either the existing welded zone 11 or the repair weld, as in the first heat-affected zone 6 and the second heat-affected zone 26. It has been found that they are more susceptible to damage due to the applied stress compared to the area in which they are present. Therefore, when the overlapping heat-affected zone 36 is generated in the repair welding, it is desirable to reduce the size of the overlapping heat-affected zone 36 as much as possible.

Therefore, in the repair welding method according to some embodiments, the size of the overlapping heat-affected zone 36 is made as small as possible as follows.
FIG. 3 is a flowchart showing a procedure for processing the repair welding method according to some embodiments. The repair welding method according to some embodiments includes a heat-affected zone shape measurement step S10, a removal range determination step S20, a removal step S30, and a repair welding step S40.
The outline flow of the repair welding method according to some embodiments is as follows. In the repair welding method according to some embodiments, the shape of the first heat-affected zone 6 is measured in the heat-affected zone shape measurement step S10, and the range to be removed from the pipe 1 is determined based on the measurement result. Determined in S20. Then, the removal range determined in the removal range determination step S20 is removed in the removal step S30, and the removed portion is repair-welded in the repair welding step S40. Hereinafter, details of each step will be described.

(Heat-affected zone shape measurement step S10)
The heat-affected zone shape measurement step S10 is a step of measuring the shape of the first heat-affected zone 6 prior to the repair welding step S40. In order to reduce the size of the overlapping heat-affected zone 36 as much as possible, it is necessary to consider what shape the repair welding region should be set to, and for that purpose, it is necessary to consider the heat of the existing welded zone 11. It is necessary to grasp the shape of the affected zone 6. Therefore, in the repair welding method according to some embodiments, the shape of the heat-affected zone 6 in the vicinity of the crack 7 is measured in the heat-affected zone shape measuring step S10.

Specifically, in the heat-affected zone shape measuring step S10, the shape of the heat-affected zone 6 in the vicinity of the crack 7 is measured by, for example, ultrasonic flaw detection by a phased array method. FIG. 4 is a diagram showing an example of a part of a cross section of a pipe 1 including a base material 2 and an existing welded portion 11. FIG. 4A is a diagram showing a macrostructure of a cross section, and FIG. 4B is a contour diagram showing the result of ultrasonic flaw detection by the phased array method of the cross section. For convenience of explanation, FIGS. 4 (a) and 4 (b) show the boundary between the base metal 2 and the weld metal 5 and the first heat-affected zone 6 with a broken line. The two-dot chain line 12 in FIG. 4B is a virtual line representing the shape of the pipe 1.

As is clear from contour FIG. 13 shown in FIG. 4 (b), the shape of the heat-affected zone 6 can be measured by ultrasonic flaw detection by the phased array method. In FIG. 13, the back surface echo 14 on the inner peripheral surface of the pipe 1 appears. Further, noise 15 and wedge noise 16 in the weld metal 5 may appear in the contour diagram 13. Therefore, it is necessary to specify the shape of the first heat-affected zone 6 in consideration of the appearance of the back surface echo 14 and the noises 15 and 16.
When inspecting the presence or absence of damage to the pipe 1 by ultrasonic flaw detection by the phased array method in the periodic inspection, information on the shape of the heat-affected zone 6 in the vicinity of the crack 7 based on the inspection result obtained by the inspection. May be obtained.

In addition to the phased array method, the shape of the heat-affected zone 6 in the vicinity of the crack 7 may be measured by ultrasonic flaw detection by another method.
In this way, by measuring the shape of the first heat-affected zone 6 by ultrasonic flaw detection such as the phased array method, the shape of the first heat-affected zone 6 can be measured non-destructively.

Further, in the heat-affected zone shape measuring step S10, the shape of the first heat-affected zone 6 may be exposed by etching, for example, and the shape of the first heat-affected zone 6 may be measured. FIG. 5 is a diagram showing an example of the surface of the pipe 1 after etching. As is clear from FIG. 5, for example, by performing etching, the position and shape of the first heat-affected zone 6 on the outer peripheral surface of the pipe 1 can be measured. The shape of the first heat-affected zone 6 inside the pipe 1 can be estimated based on the design information regarding the existing welded portion 11 such as the groove shape.
By exposing the shape of the first heat-affected zone 6 on the surface of the pipe 1 by a simple method of etching, the shape of the first heat-affected zone 6 can be easily measured.
If the crossing angle between the first heat-affected zone 6 and the second heat-affected zone 26 can be set to a desired angle as described later without measuring the shape of the first heat-affected zone 6. The heat-affected zone shape measurement step S10 described above does not necessarily have to be performed.

(Removal range determination step S20)
The removal range determination step S20 is a step of determining the removal range in the removal step S30 based on the shape of the first heat-affected zone 6 measured in the heat-affected zone shape measurement step S10.
For example, as shown in FIG. 9, in the cross section of the pipe 1 including the base metal 2 and the existing welded portion 11, the first heat-affected zone 6 is located on the base metal 2 side from the boundary surface along the boundary surface in contact with the weld metal 5. It is formed with a constant width W1 toward. Similarly, in the cross section of the pipe 1 including the base metal 2 and the existing welded portion 11, the second heat-affected zone 26 is formed with a constant width W2 along the boundary surface in contact with the weld metal 25 of the repair welding. Therefore, if the intersection angles θ1 to θ5 between the first heat-affected zone 6 and the second heat-affected zone 26 in the cross section of the pipe 1 including the base metal 2 and the existing welded zone 11 are 90 degrees, the first heat-affected zone The cross-sectional area of the intersection of 6 and the second heat-affected zone 26, that is, the overlapping heat-affected zone 36 can be minimized. On the contrary, as the intersection angles θ1 to θ5 between the first heat-affected zone 6 and the second heat-affected zone 26 deviate from 90 degrees, the cross-sectional area of the overlapping heat-affected zone 36 becomes larger.

Therefore, in the removal range determination step S20 according to some embodiments, the intersection angles θ1 to θ5 between the first heat-affected zone 6 and the second heat-affected zone 26 are set to 70 degrees or more and 110 degrees or less, and The removal range in the removal step S30 is determined so as to remove the crack 7.
Specifically, in the removal range determination step S20 according to some embodiments, a constant width W2 is provided on the inner side of the member constituting the pipe 1 from the surface that appears after removing a part of the pipe 1 in the removal step S30. Considering that the second heat-affected zone 26 is formed, the removal in the removing step S30 is such that the intersection angle between the first heat-affected zone 6 and the second heat-affected zone 26 is 70 degrees or more and 110 degrees or less. Determine the range.

For example, in the removal range determination step S20 according to the embodiment, as shown in FIG. 6, not only a part of the heat-affected zone 6 on the first end 3 side where the crack 7 is generated but also the crack 7 is generated. A part of the heat-affected zone 6 on the side of the second end 4 that was not present is also determined as the removal range 40. Note that FIG. 6 is a diagram schematically showing a part of a cross section of the pipe 1 after removing the removal range 40 in the removal step S30 described below, including the base material 2 and the existing welded portion 11.
In the embodiment shown in FIG. 6, the bottom surface of the removal range 40, that is, the surface 41 extending in the circumferential direction (horizontal direction in the drawing) among the surfaces appearing after the removal range 40 is removed, is schematically shown in FIG. As shown, it may be flat, and although it is not shown, it may be curved around the axis of the pipe 1, and the removal range 40 is deeper toward the center in the circumferential direction than when it is flat. You may make it deeper.

Further, in one embodiment shown in FIG. 6, the side surface of the removal range 40, that is, the surface that appears after the removal range 40 is removed, extends in the thickness direction (vertical direction in the drawing) of the base material 2. As schematically shown in FIG. 6, the surface 42 on the 1st end 3 side and the surface 42 on the 2nd end 4 side extend in substantially the same direction as the thickness direction of the base material 2 from the outer peripheral surface 1a of the pipe 1. The extension direction may be set so that the removal range 40 is present and the removal range 40 becomes narrower toward the inner side in the radial direction of the pipe 1.
The removal range 40 is narrowed by bringing the extending direction of the surface 42 on the first end 3 side and the surface 42 on the second end 4 side closer to the thickness direction of the base metal 2 (diameter direction of the pipe 1). That is, the range of repair welding can be narrowed, and the man-hours required for removal and repair welding can be suppressed.

For example, in the removal range determination step S20 according to another embodiment, as shown in FIG. 7, a part of the heat-affected zone 6 on the first end portion 3 side where the crack 7 is generated is determined as the removal range 40. Note that FIG. 7 is a diagram schematically showing a part of a cross section of the pipe 1 after removing the removal range 40 in the removal step S30 described below, including the base material 2 and the existing welded portion 11.
In the embodiment shown in FIG. 7, the surface 41 may be planar as schematically shown in FIG. 7, as in the case of the one embodiment shown in FIG. 6, and although not shown, the pipe 1 It may be a curved surface centered on the axis of.

Further, in the other embodiment shown in FIG. 7, the surface 42 on the first end portion 3 side and the surface 42 formed on the weld metal 5 are shown in FIG. 7 as in the case of the one embodiment shown in FIG. As schematically shown, it extends from the outer peripheral surface 1a of the pipe 1 in substantially the same direction as the thickness direction of the base metal 2, and the removal range 40 becomes narrower toward the inner side in the radial direction of the pipe 1. The extension direction may be set.

For example, in the removal range determination step S20 according to still another embodiment, as shown in FIG. 8, not only a part of the heat-affected zone 6 on the first end 3 side where the crack 7 has occurred but also the crack 7 is formed. A part of the heat-affected zone 6 on the side of the second end 4 that did not occur is also determined as the removal range 40. Note that FIG. 8 is a diagram schematically showing a part of a cross section of the pipe 1 after removing the removal range 40 in the removal step S30 described below, including the base material 2 and the existing welded portion 11.
In the embodiment shown in FIG. 8, the surface 41 is the first surface 41a inclined so as to approach a direction orthogonal to the extending direction of the heat-affected zone 6 on the first end 3 side, and the second end 4 side. It includes a second surface 41b inclined so as to approach a direction orthogonal to the extending direction of the heat-affected zone 6. That is, in still another embodiment shown in FIG. 8, the heat-affected zone 6 on the first end 3 side and the heat-affected zone 6 on the second end 4 side, which have slightly different extending directions, are combined. , The extending direction of the first surface 41a and the extending direction of the second surface 41b are individually set.

Further, in still another embodiment shown in FIG. 8, the surface 42 on the first end 3 side and the surface 42 on the second end 4 side are the same as in the case of one embodiment shown in FIG. As schematically shown in 8, the removal range 40 extends from the outer peripheral surface 1a of the pipe 1 in substantially the same direction as the thickness direction of the base material 2, and the removal range 40 becomes narrower toward the inner side in the radial direction of the pipe 1. In addition, the extension direction may be set.

As described above, since the repair welding method according to some embodiments includes the heat-affected zone shape measurement step S10 and the removal range determination step S20, the intersection of the first heat-affected zone 6 and the second heat-affected zone 26 The removal range 40 can be set and removed so that the angle is 70 degrees or more and 110 degrees or less. As a result, it is possible to suppress an increase in the cross-sectional area of the overlapping heat-affected zone 36 in the cross section including the base metal 2 and the existing welded portion 11, and it is possible to suppress a decrease in the life of the pipe 1 due to repair welding.

(Removal step S30)
The removal step S30 is a step of removing a portion of the existing welded portion 11 including at least a part of the first heat-affected zone 6.
In the removal step S30, for example, a grinding tool such as a grinder is used to remove the removal range 40 determined in the removal range determination step S20 from the pipe 1. As described above, the pipe 1 after removing the removal range 40 in the removal step S30 has a cross-sectional shape as shown in FIGS. 6 to 8.

(Repair welding process S40)
The repair welding step S40 is a step of performing repair welding after removing the removal range 40.
In the repair welding step S40 according to the embodiment, repair welding is performed as shown in FIG. Note that FIG. 9 is a diagram schematically showing a part of a cross section of the pipe 1 including the base material 2 and the existing welded portion 11, and the removal range 40 shown in FIG. 6 is removed in the removal step S30 according to the embodiment. It is a figure which shows the case where the repair welding is performed after that.
In the repair welding step S40 according to another embodiment, repair welding is performed as shown in FIG. Note that FIG. 10 is a diagram schematically showing a part of a cross section of the pipe 1 including the base material 2 and the existing welded portion 11, and the removal range 40 shown in FIG. 7 in the removal step S30 according to another embodiment is shown. It is a figure which shows the case where repair welding was performed after removal.
In the repair welding step S40 according to still another embodiment, repair welding is performed as shown in FIG. Note that FIG. 11 is a diagram schematically showing a part of a cross section of the pipe 1 including the base material 2 and the existing welded portion 11, and the removal range 40 shown in FIG. 8 in the removal step S30 according to another embodiment. It is a figure which shows the case where the repair welding is performed after removing.
For convenience of explanation, in FIGS. 9 to 11, the position where the first heat-affected zone 6 of the existing welded portion 11 was present is represented by a two-dot chain line.

The pipe 1 after the repair welding is performed in the repair welding step S40 according to some embodiments has the following characteristics. In other words, the removal range 40 is determined in the removal range determination step S20 so that the pipe 1 after repair welding has the following characteristics.

In some embodiments shown in FIGS. 9 to 11, in the cross section including the base metal 2 and the existing welded zone 11, the first heat-affected zone 6 in the existing welded zone 11 and the second heat-affected zone 26 by repair welding are provided. At all the intersections (overlapping heat-affected zone 36), the intersection angles θ1 to θ5 between the first heat-affected zone 6 and the second heat-affected zone 26 are 70 degrees or more and 110 degrees or less.

In the cross section including the base metal 2 and the existing welded portion 11, the intersection (overlapping heat affected zone 36) between the first heat affected zone 6 of the existing welded portion 11 and the second heat affected zone 26 of the repair welded portion 21 is described above. As described above, since it is easily damaged by the acting stress, it is desirable to prevent the overlapping heat-affected zone 36 from being generated as much as possible.
Further, as described above, in the cross section including the base metal 2 and the existing welded zone 11, the first heat-affected zone 6 and the second heat-affected zone 26 have a constant width along the boundary surface in contact with the weld metals 5 and 25, respectively. Since it is formed by W1 and W2, if the intersection angles θ1 to θ5 between the first heat-affected zone 6 and the second heat-affected zone 26 are 90 degrees, the cross-sectional area of the overlapping heat-affected zone 36 should be minimized. The more the crossing angles θ1 to θ5 deviate from 90 degrees, the larger the cross-sectional area of the overlapping heat-affected zone 36 becomes.
In that respect, in some embodiments shown in FIGS. 9 to 11, since the cross-sectional angles θ1 to θ5 between the first heat-affected zone 6 and the second heat-affected zone 26 are 70 degrees or more and 110 degrees or less, the base material. It is possible to prevent the cross-sectional area of the overlapping heat-affected zone 36 from becoming large in the cross section including the existing welded portion 11. As a result, it is possible to suppress a decrease in the life of the pipe 1 due to repair welding.

In the embodiment shown in FIGS. 9 and 11, in the cross section including the base material 2 and the existing welded portion 11, the repair welding is performed from the base material 2 on the first end portion 3 side to the base material 2 on the second end portion 4 side. Will be done.
Then, the first heat-affected zone 6 generated on the base material 2 on the first end 3 side and the first heat-affected zone generated on the base material 2 on the second end 4 side before the removal range 40 is removed. It occurs in the second heat-affected zone 26 generated in the base material 2 on the first end 3 side and the base material 2 on the second end 4 side with respect to the first interval d1 on the surface of the base material 2 with 6. The second interval d2 on the surface of the base material 2 with the second heat-affected zone 26 is 1.1 times or more and 2.0 times or less the first interval d1.
By setting the second interval d2 to 1.1 times or more the first interval d1, it is possible to prevent the first heat-affected zone 6 and the second heat-affected zone 26 from overlapping in the vicinity of the surface of the base material 2. Further, by setting the second interval d2 to 2.0 times or less the first interval d1, the range of repair welding can be suppressed.

In one embodiment shown in FIG. 9, in the cross section including the base material 2 and the existing welded portion 11, the repair welding is performed from the base material 2 on the first end portion 3 side to the base material 2 on the second end portion 4 side. ..
The third distance d3 between the overlapping heat-affected zone 36 on the first end 3 side and the overlapping heat-affected zone 36 on the second end 4 side is from the surface of the weld metal 25 in the second heat-affected zone 26. The position P1 on the first end 3 side, which is 0.8 times the maximum depth hmax of the depth h to the second heat-affected zone 26, and the second, which is 0.8 times the maximum value hmax. It is the fourth distance d4 or less from the position P2 on the end 4 side.

As a result, the depth H of the overlapping heat-affected zone 36 on the first end 3 side and the overlapping heat-affected zone 36 on the second end 4 side is repaired. It can be 0.8 times or more the maximum value hmax of the h. As a result, in the cross section including the base metal 2 and the existing welded portion 11, the positions of the overlapping heat-affected zone 36 on the first end 3 side and the overlapping heat-affected zone 36 on the second end 4 side in the depth direction are second. It can be approached to the deepest position in the heat-affected zone 26. Therefore, the extending direction of the second heat-affected zone 26 in the overlapping heat-affected zone 36 on the first end 3 side and the overlapping heat-affected zone 36 on the second end 4 side is brought closer to the direction orthogonal to the depth direction. be able to. Therefore, if the first heat-affected zone 6 in the overlapping heat-affected zone 36 extends in substantially the same direction as the depth direction, the intersection angles θ1 and θ2 in the overlapping heat-affected zone 36 can be brought close to 90 degrees. It is possible to prevent the cross-sectional area of the overlapping heat-affected zone 36 from becoming large.

In one embodiment shown in FIG. 9, in the cross section including the base metal 2 and the existing welded portion 11, the extending direction of the second heat-affected zone 26 generated by repair welding to the weld metal 5 of the existing welded portion 11 and the pipe 1 The cross-sectional angle θ6 with the thickness direction of is 70 degrees or more and 110 degrees or less.

The second heat-affected zone 26 in the weld metal 5 of the existing weld 11 acts more than the second heat-affected zone 26 of the base metal 2 and the weld metal 5 of the existing weld 11 that is not affected by the heat of the repair welding. It is easily damaged by the stress. Therefore, when the tensile stress acts on the pipe 1 in the circumferential direction, that is, in the direction in which the first end portion 3 side and the second end portion 4 side are separated from each other, when viewed from the direction in which the tensile stress acts. It is desirable that the projected area of the second heat-affected zone 26 in the weld metal 5 of the existing welded portion 11 is small.
In that respect, in one embodiment shown in FIG. 9, the intersection angle θ6 between the extending direction of the second heat-affected zone 26 in the weld metal 5 of the existing welded portion 11 and the thickness direction of the pipe 1 is 70 degrees or more 110. Since it is less than or equal to the degree, the extending direction of the second heat-affected zone 26 in the weld metal 5 of the existing welded portion 11 approaches the direction in which the above-mentioned tensile stress acts, and the projected area can be suppressed.

In the embodiment shown in FIGS. 9 and 11, the weld toe portion 23 for repair welding is present in the base metal 2. Further, in the embodiment shown in FIG. 10, the weld toe portion 23 on the first end portion 3 side of the repair welding is present in the base metal 2.
As a result, the region of the second heat-affected zone 26 in the weld metal 5 can be reduced as compared with the case where the weld toe portion 23 of the repair welding exists in the weld metal 5 of the existing weld portion 11.

In the embodiment shown in FIG. 10, in the cross section including the base metal 2 and the existing welded portion 11, repair welding is performed from the base metal 2 on the first end portion 3 side to the weld metal 5 of the existing welded portion 11.
Then, the position P3 of the second heat-affected zone 26 appearing on the surface of the base metal 2 on the first end portion 3 side and the position P4 of the second heat-affected zone 26 appearing on the surface of the weld metal 5 of the existing welded portion 11. The intermediate position C1 exists in the weld metal 5 of the existing weld portion 11 before the removal range 40 is removed.
As a result, the amount of removal in the removal step S30 and the volume of the weld metal 25 by repair welding can be reduced while suppressing the increase in the cross-sectional area of the overlapping heat-affected zone 36, and the man-hours for repair welding can be reduced. Can be reduced.

In the embodiment shown in FIG. 11, in the cross section including the base material 2 and the existing welded portion 11, the repair welding is performed from the base material 2 on the first end portion 3 side to the base material 2 on the second end portion 4 side. Further, in the embodiment shown in FIG. 11, the first heat-affected zone 6 on the first end 3 side is the outer peripheral surface of the pipe 1 at least at the intersection with the second heat-affected zone 26 (overlapping heat-affected zone 36). It is inclined with respect to the radial direction of the pipe 1 so as to be located on the second end 4 side as the distance from 1a increases. In the embodiment shown in FIG. 11, the first heat-affected zone 6 on the second end 4 side is at least at the intersection with the second heat-affected zone 26 (overlapping heat-affected zone 36) from the outer peripheral surface 1a of the pipe 1. As the distance increases, the pipe 1 is inclined with respect to the radial direction so as to be located on the side of the first end portion 3.
Then, in the embodiment shown in FIG. 11, the second heat-affected zone 26 is at least at the intersection with the first heat-affected zone 6 on the first end 3 side (overlapping heat-affected zone 36). The depth from the outer peripheral surface 1a of the pipe 1 becomes shallower from the side toward the second end portion 4 side. In the embodiment shown in FIG. 11, the second heat-affected zone 26 is at least at the intersection with the first heat-affected zone 6 on the second end 4 side (overlapping heat-affected zone 36) from the second end 4 side. The depth from the outer peripheral surface 1a of the pipe 1 becomes shallower toward the first end 3 side.
As a result, the intersection angles θ4 and θ5 in the overlapping heat-affected zone 36 can be brought close to 90 degrees, and it is possible to suppress an increase in the cross-sectional area of the overlapping heat-affected zone 36.

The repair welding method according to some of the above-described embodiments is suitable for repair welding of the pipe 1 having the longitudinal welded portion 10 of the pipe 1.
The repair welding method according to some of the above-described embodiments is suitable for repair welding of high-temperature pipes of boilers and turbines in, for example, thermal power / nuclear power plants and chemical plants. Such high-temperature pipes are important pipes that are used for a long period of time in a high-temperature environment and are expected to have a significant effect on the operation of the plant if breakage or the like occurs. Further, since such high-temperature piping is generally inspected or repaired at a limited time such as periodic inspection, it is required to be able to be used for a long period of time. In addition, such high-temperature piping may take a long time to obtain in terms of material, thickness, and the like. Therefore, if the crack 7 or the like of the pipe 1 can be repaired by the repair welding method according to some of the above-described embodiments within a limited period such as a periodic inspection, the economic effect is great.

In the above description, the material of the pipe 1 is not particularly mentioned, but in the repair welding method according to some embodiments, the decrease in strength in the overlap heat affected zone 36 tends to be a problem, and the strength is high. Suitable for repair welding of members made of ferritic heat resistant steel.
Here, the high-strength ferritic heat-resistant steel is referred to as, for example, Gr. Equivalent material of 91 series steel (Tue SCMV28, Tue STPA28, Tue SFVAF28, Tue STBA28), Gr. Equivalent material of 92 series steel (Tue STPA29, Tue SFVAF29, Tue STBA29), Tue Gr. Equivalent material of 122 series steel (Tue SUS410J3, Tue SUS410J3TP, Tue SUSF410J3, Tue SUS410J3TB, Tue SUS410J3DTB) or Gr. It is an equivalent material of 23 series steel (fire STPA24J1, fire SFVAF22AJ1, fire STBA24J1, fire SCMV4J1).
The material of the pipe 1 is not limited to high-strength ferritic steel, and may be, for example, low alloy steel or stainless steel. The low alloy steel is, for example, an equivalent material of STBA12, an equivalent material of STBA13, an equivalent material of STPA20, an equivalent material of fire STPA21, an equivalent material of STPA22, an equivalent material of STPA23, or an equivalent material of STPA24. The stainless steel is, for example, SUS304TP equivalent material, SUS304LTP equivalent material, SUS304HTP equivalent material, fire SUS304J1HTB equivalent material, SUS321TP equivalent material, SUS321HTP equivalent material, SUS316HTP equivalent material, SUS347HPP equivalent material, or It is an equivalent material of Tue SUS310J1TB.

The present invention is not limited to the above-described embodiment, and includes a modification of the above-mentioned embodiment and a combination of these embodiments as appropriate.
For example, in some of the above-described embodiments, the repair method in the longitudinal welded portion 10 of the pipe 1 has been described as an example, but the present invention is not limited thereto. The repair welding method according to some of the above-described embodiments is applied to repair welding of other welded parts such as a circumferential welded part connecting pipes and a pedestal welded part connecting pipes and branch pipes. May be good. Further, the repair welding method according to some of the above-described embodiments may be applied to repair welding of welded portions of other members such as plate materials other than pipes.

1 High temperature piping (piping)
2 Base metal 3 1st end 4 2nd end 5,25 Welded metal 6 Heat-affected zone (1st heat-affected zone)
7 Crack 10 Longitudinal weld 11 Existing weld 21 Repair weld 23 Weld toe 26 Heat-affected zone (second heat-affected zone)
36 Intersection (overlapping heat affected zone)

Claims (10)

It is a repair welding method for members in which the first end and the second end of the base metal are connected by welding.
A step of removing a portion including at least a part of the first heat-affected zone in the existing welded portion of the member.
The process of performing repair welding after removing the above-mentioned part, and
Equipped with
In the cross section including the base metal and the existing welded portion, the first heat-affected zone and the said A repair welding method in which the cross-sectional angle with the second heat-affected zone is 70 degrees or more and 110 degrees or less. In the cross section including the base material and the existing welded portion, the repair welding is performed from the base material on the first end side to the base material on the second end side.
The first heat-affected zone generated in the base material on the first end side and the base material on the second end side before removing the portion including at least a part of the first heat-affected zone. The second heat-affected zone generated on the base material on the first end side and the second end portion with respect to the first distance on the surface of the base material between the first heat-affected zone and the first heat-affected zone. The second distance on the surface of the base material with the second heat-affected zone generated on the base material on the side is 1.1 times or more and 2.0 times or less the first distance.
The repair welding method according to claim 1. In the cross section including the base material and the existing welded portion, the repair welding is performed from the base material on the first end side to the base material on the second end side.
The third distance between the intersection on the first end side and the intersection on the second end side is the second heat from the surface of the weld metal of the repair weld in the second heat-affected zone. The position on the first end side, which is 0.8 times the maximum depth to the affected area, and the position on the second end side, which is 0.8 times the maximum depth. The repair welding method according to claim 1 or 2, wherein the interval is 4 or less. In the cross section including the base metal and the existing welded portion, the crossing angle between the extending direction of the second heat-affected zone generated by the repair welding on the weld metal of the existing welded portion and the thickness direction of the member is determined. The repair welding method according to any one of claims 1 to 3, wherein the temperature is 70 degrees or more and 110 degrees or less. The repair welding method according to any one of claims 1 to 4, wherein the weld toe portion of the repair welding is present in the base metal. In the cross section including the base metal and the existing welded portion, the repair welding is performed from the base metal on the first end side to the weld metal of the existing welded portion.
The intermediate position between the position of the second heat-affected zone appearing on the surface of the base metal on the first end side and the position of the second heat-affected zone appearing on the surface of the weld metal of the existing welded portion is The repair welding method according to claim 1, which is present in the weld metal of the existing welded zone before removing a portion including at least a part of the first heat-affected zone. Prior to the repair welding step, the step of measuring the shape of the first heat-affected zone and the step of measuring the shape of the first heat-affected zone
Based on the shape of the first heat-affected zone measured in the step of measuring the shape of the first heat-affected zone, the removal range in the step of removing the portion including at least a part of the first heat-affected zone is determined. Process and
The repair welding method according to any one of claims 1 to 6, further comprising. In the step of measuring the shape of the first heat-affected zone, the shape of the first heat-affected zone is measured by ultrasonic flaw detection by the phased array method, or the shape of the first heat-affected zone is revealed by etching. The repair welding method according to claim 7, wherein the shape of the first heat-affected zone is measured. The repair welding method according to any one of claims 1 to 8, wherein the base material is a high-strength ferritic heat-resistant steel. The repair welding method according to any one of claims 1 to 9, wherein the member is a boiler pipe.

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